Obviously, it requires only one subject, one
participant. But that’s a misnomer to think that single-subject is just about one participant.
You can have as many as twenty or thirty. I think a lot of students are in clinic used
to the measurement of one pre-test and one post-test because of the way the goals are
written, and maybe there’s not enough time to collect continuous data. But single-case experimental designs require
ongoing data collection. There’s this misperception that one baseline datapoint is enough. But
for single-case experimental design you want to see at least three datapoints, because
it allows you to see a trend in the data. So there’s a myth about the number of datapoints
needed. The more datapoints we have, the better. Single-subject design has it’s own tradition
of methodology. It seems very easy to do when you read up on one design. But there are lots
of things to consider, and lots of things can go wrong. It requires quite a bit of training. It takes
at least one three-credit course that you take over the whole semester.